1. Field of the Invention
The present invention is directed to a liquid jet type recording head, a method for manufacturing the same, and a liquid jet type recording apparatus, and more specifically to a liquid jet type recording head used in a thermal type liquid ejector apparatus capable of continuously and stably jetting (printing) liquid at high speed, a method of manufacturing the same, and a liquid jet type recording apparatus using the same.
2. Description of the Related Art
Recently, the liquid jet recording apparatus has attracted a great deal of public attention because of its nature as a low-cost and high quality color recording apparatus. Exemplary liquid jet recording heads for use in the liquid jet recording apparatus includes, for example, a piezo-electric liquid jet recording head for jetting liquid through nozzles with the pressure generated by the mechanical distortion of pressure chamber by a piezo-electric element, and a thermal type liquid jet recording head for jetting liquid through nozzles with the pressure generated by evaporation of liquid by applying current to heating elements each of which is individually arranged in a separate channel.
There are some known ink jet printing heads in the Prior Art. Japanese Published Unexamined Patent Application No. Hei 9-226142 discloses the prevention of bubbles by providing an ink supplying channel having smaller cross-sectional area than the cross section of opening of the common ink chamber for an ink supplying channel to the common ink chamber communicating with the head orifice of the printing head. Japanese Published Unexamined Patent Application No. Hei 11-227208 discloses narrowing in the vertical direction the inner walls of head in the proximity of nozzles and liquid inlet within each orifice in the recording head to improve the ink supply. Japanese Published Unexamined Patent Application No. Hei 1-148560 discloses a method of creating an ink jet recording head by compiling a first substrate having ink channels and a common chamber formed by anisotropic etching on a surface side of silicon wafer, and a second substrate having heating elements and addressing electrodes formed on a surface side of silicon wafer. Japanese Published Unexamined Patent Application No. Hei 5-338177 discloses a printing head with a fitting arrangement of an ink manifold used as the common liquid chamber of recording head with an ink reservoir, having the back end wall of ink manifold formed as a sharp edge. Japanese Published Unexamined Patent Application No. Hei 5-338168 discloses a method of removing bubbles in a reservoir by forming an ink supplying lid of parallelogram to an ink reservoir of a printing head made of a silicon substrate. Japanese Published Unexamined Patent Application No. Hei 8-118666 discloses an ink jet recording head by forming an ink jet recording head chip by bonding plural silicon substrates, removing a part of one of silicon substrates of the head chip, and providing a common ink chamber having an ink supplying opening at the removed part. Japanese Published Unexamined Patent Application No. Hei 8-118653 discloses a method of improving the adhesiveness between silicon substrates in an inkjet printing head having two patterned silicon substrates bonded together by an intermediate thick film of a polymer by flattening by chemically or mechanically polishing the intermediate thick film layer of the ink jet printing head.
An example of the thermal type liquid jet recording head of the state of the art is disclosed in the Japanese Published Unexamined Patent Application No. Hei 9-226142. Now referring to FIG. 20, there is shown a perspective view of a liquid jet recording head and a liquid supplier incorporated in a liquid jet recorder of the Prior Art. FIG. 21 depicts a cross-sectional view of the head shown in FIG. 20 taken along with the line Axe2x80x94A.
A head chip 100 has plural channels 102 formed in parallel at a predetermined distance, and an ink outlet 104 is outwardly opened at an end of each channel 102. The other end of each of plural channels 102 is communicated with a commonly shared ink chamber 106. At the top of ink chamber 106 an opening 108 is formed for supplying liquid thereto. In each of channels 102 a heating element 110 is disposed, which generates heat to foam the liquid in the channel 102, and the pressure generated by the foamed liquid forces the liquid to eject through the ink outlet 104 for recording.
The head chip 100 as has been described above may be formed by bonding a heating element substrate 114 with heating elements 110 mounted thereon and a channel substrate 116 having grooves formed for the channels 102 and the common ink chamber 106, with the aid of a resin layer (not shown in the figure).
The heating element substrate 114 is affixed to a heat sink 118 for effective radiation of heat. On the heat sink 118 is formed a printed circuitry to transfer power and signals supplied from the liquid jet recorder through the bonding wires 120 to the heating element substrate 114 and to feed back signals generated by a variety of sensors incorporated in the heating element substrate 114 to the recorder.
On the head chip 100, a liquid supplier member 122 is bonded. The liquid supplier member 122 includes liquid channels 124 for supplying liquid from a liquid reservoir (not shown) to the head chip 100.
The liquid jet recording head thus formed will be supplied with liquid from the liquid reservoir through the separate channels 102. In other words, the liquid supplied from the reservoir will flow through the liquid channels 124 of the liquid supplier member 122, then through the liquid inlet 108 opened on the top of the channel substrate 116 of the head chip 100 to the common chamber 106, in order to supply ultimately to each of the separate channels 102.
In a liquid jet recording head as has been described above has a disadvantage that some bubbles will be intermixed with the liquid when introducing the liquid from the liquid reservoir to the liquid chamber 106. The bubbles mixed therein along with the liquid tend to reside intensively in the area 126 (see FIG. 21) in the liquid chamber 106 where the liquid flow is slow. In case where bubbles reside in the chamber 106 for example, the bubbles will grow larger while repeatedly jetting the liquid so as to interfere the supply of liquid by blocking channels 102, to ultimately cause the defects of recording. In the thermal type of liquid jet recording heads, the temperature of liquid will increase with the heating of heating element 110. As the result of heating the air dissolved in the liquid, bubbles will be deposited in the common chamber 106 and enlarged to be likely to prevent smooth ejection of liquid drops therefrom. In this manner, heating may develop bubbles in the common chamber 106 as well as in the junction of the common chamber 106 with the liquid supplier member 122, resulting in a problem of blocking by bubbles.
In order to purge bubbles residing in the common liquid chamber, it is common to aspirate through the nozzles 104. When sucking bubbles through the nozzles 104, an amount of liquid equivalent to the volume sucked will be supplied from the reservoir. Thus supplied liquid will spread along with the shape of the common liquid chamber 106 to be directed to the separate channels 102. The liquid flow may force bubbles to advance toward the channels 102 to purge from the nozzles 104. However, the bubbles residing at both ends of the chamber 106, at the ends shown by the arrow in the direction of X, which are the primary cause of defects in the printing quality, are difficult to be completely removed because these bubbles are in the area of very slow flow of liquid.
In order to remove bubbles residing at both ends of the chamber 106 as has been described above, in the liquid jet recording heads of the Prior Art, dummy nozzles 126 have to be provided at both ends of the chamber 106, which nozzles are not for use in printing.
Although it is conceivable to increase the number of times of aspiration through nozzles, there will arise problems that a higher frequency of aspiration cleaning decreases the effective efficiency of liquid for use in recording, and requires a larger volume of a waste liquid container for containing aspired waste liquid, resulting In a larger apparatus in size.
In a thermal type liquid jet recording head, there is another problem that high speed and continuous printing cannot be performed. This is because when ejection (recording) is continuously performed, the temperature of head assembly increases to ultimately disable the stable ejection of liquid.
In order to avoid this phenomenon, finer control of printing such as stopping printing at or beyond a predetermined temperature threshold or slowing the speed of printing by monitoring the temperature of the head will be required.
The present invention has been made in view of the above circumstances and provides a liquid jet printing head, a method of manufacturing the same, and a liquid jet recording apparatus using the same.
In order to solve the above mentioned problems, the present invention provides a liquid jet printing head for jetting liquid by heating with a heater member, includes: a common liquid chamber having an inlet opening for supplying liquid from outside; and plural separated channels for heating liquid supplied through the chamber with the heating elements to eject the liquid through outlets; a heating element substrate incorporating plural heating elements; wherein the liquid supplied from the inlet flows through linearly to the outlet, and wherein the heating element substrate is arranged along with the flow of the liquid.
Now the function of an aspect of the present invention will be described in greater details below.
The liquid that has reached to the common chamber through the inlet will flow through each of separate channels, be heated by heating elements each provided for a channel, and ejected as liquid drops due to the pressure of bubbles generated by heating. The liquid that has flowed through the common chamber from the inlet will be introduced linearly to the channels along with the surface of heating elements formed on the heating element substrate so as to be ejected through the outlet. Because a smooth flow of liquid from the inlet through the channel is achieved, bubbles created in the separate channels or in the chamber will be evacuated smoothly to the atmosphere together with the liquid drops. By arranging the ejection of liquid in the direction of gravity, the bubbles generated will move to the top of common chamber, then through the inlet to the liquid reservoir. This arrangement will prevent the ejection of liquid from being blocked by residing and growing in the proximity of separate channels and by finally occluding separate channels.
Since the liquid flows through along with the surface of heating elements formed on the heating element substrate, the substrate will be effectively cooled down by the liquid so as to be able to suppress the increase of temperature in the heating element substrate.
Therefore a stable, high speed, continuous liquid jet (printing) will be performed.
Another aspect of the present invention is characterized in that a liquid jet printing head further includes a guiding surface for driving the liquid that flows through the common chamber to the separate channels.
Now the function of the present invention will be described in greater details below.
A guiding surface is formed from the common chamber to the channels, so that the liquid will flow there through smoothly. This ensures that the bubbles generated in the common chamber will not remain in the chamber and will be securely ejaculated through the channels.
Another aspect of the present invention is characterized in that a liquid jet printing head further includes a guide plate provided for narrowing the cross section of path toward the channels.
The function of the invention will be described in greater details below.
A guide plate is provided for narrowing the cross section of flow path from the common chamber toward the separate channels, thereby the flow of liquid entering from the common chamber to the separate channels will be accelerated. This allows the liquid flow entering to separate channels to be smoother, resulting in easier evacuation of bubbles generated in the common chamber or separate channels, in other words secure prevention of residual bubbles in the proximity of separate channels. In addition this promotes cooling of the heating element substrate so as to enable more effective control of temperature increase.
Still another aspect of the present invention is characterized in that, in a liquid jet printing head, the cross section of path formed by the guide plate and the substrate is gradually diminished in the direction toward the separate channels.
The function of the invention will be description in greater details below.
The decrease in cross section of the path formed by the guide plate and the substrate toward the separate channels causes the liquid to flow faster toward the channels, thereby the bubbles generated in the proximity of channels will be easily removed and the blocking of liquid jet will be prevented.
Another aspect of the present invention is characterized in that in a liquid jet printing head in accordance with the present invention, a liquid element substrate is arranged so as to contact liquid in the surfaces other than that of forming the heating elements in the heating element substrate.
The function of the invention will be described in greater details below.
In the present invention, a heating element substrate arranged so as to contact liquid in other surfaces in addition to the surface having heating elements may increase radiation of the heating element substrate, allowing more effective control of temperature increase caused by the heating of the heating elements. Thus more stable liquid jet may be achieved even when continuous, high-speed liquid jet is required.
Another aspect of the present invention is characterized in that a liquid jet printing head further includes a structure incorporating the separate channels together with the common chamber.
The function of the aspect of the present invention will be described in greater details below.
Separate channels incorporated with the common chamber enables the decrease in the number of parts as well as miniaturization of printing head.
If the respective separate channels are directly communicate with the common liquid chamber, bubbles remaining in the common chamber will effectively diminished because so-called dead circulate portion of the liquid in the chamber and thus, to ensure the ejection of the liquid droplet from the outlets. Also, the common chamber has relatively high volume compare to the conventional one, contacting area of the heating element substrate with the liquid will be drastically increased, and thus the heat energy generated by the heating element will be effectively released through the liquid. The heat energy released into the liquid also generate the circulate of the liquid for diminishing the temperature of the substrate.
Another aspect of the present invention is characterized in that a liquid jet printing head including input/output terminals of electric signal mounted on the surface of the heating element substrate is positioned at an end of the heating element substrate in the direction orthogonal to the direction of liquid jet.
Now the function of the invention will be described below.
In the present invention, input/output terminals of electric signals are arranged at an end of the heating element substrate in the direction orthogonal to the direction of liquid jet. The inlet of the common liquid chamber, which may be referred as a sub ink tank, may be thereby designed inline toward the separate channels. As a result, more smooth flow may be achieved with input/output terminals of electric signals arranged on the heating element substrate.
Another aspect of the present invention is characterized in that a liquid jet printing head having the surface of the heating element substrate forming the separate channels and coated by a liquid resistant resin layer, includes a liquid resistant and high thermal conductive material deposited at least on a portion of the surface of the heating elements in the heating element substrate, and a resin layer deposited on the surface of the heating elements or on the top of the high thermal conductive material such that a part of the high thermal conductive material is exposed, wherein the liquid comes in contact with the high thermal conductive material.
The function of the invention will be described below.
By depositing a film of liquid resistant resin on the heating element substrate, the corrosion of heating element substrate by the liquid will be prevented. However, coating by a resin layer will decrease the heat radiation from the heating element substrate to the liquid hence promotes the increase of temperature in the heating element substrate. Therefore, by depositing a liquid resistant and high thermal conductive material to at least on a portion of the heating element substrate and exposing a portion of the high thermal conductive material to the liquid to come in contact therewith, the heat generated in the heating element substrate will be effectively conducted to the liquid through the high thermal conductive material. In other words, in accordance with the present invention, the increase of temperature in the heating element substrate will be sufficiently controlled so as to enable stable, high speed, and continuous liquid jet.
Another aspect of the present invention is characterized in that a liquid jet printing head further includes plural openings in the resin layer for exposing the high thermal conductive material.
The function of the invention will be described below.
In order to promote heat radiation from the heating element substrate to the liquid, it may be needed to increase the exposed surface area of the high thermal conductive material. This means that larger area of opening in the resin layer is better. However, when polishing for flattening the surface of the resin layer, there may arise a problem that some abrasive may penetrate into the opening, and the area in proximity of the opening may be locally polished. In accordance with the present invention, there are plural openings provided; the polishing of resin layer may be entirely leveled to increase the radiation.
Another aspect of the present invention is characterized in that a liquid jet printing head further includes the openings of the same shape as the holes provided in the resin layer for exposing the heating elements.
The function of the invention will be described below.
The openings, which have the same shape as the holes formed in the resin layer in order to expose the heating elements, may further level the polishing of the resin layer.
Another aspect of the present invention is characterized in that a liquid jet printing head further includes the openings arranged in a staggered pattern.
The function of the invention will be described below.
The staggered pattern of the openings allows the polished state of resin layer to be further leveled.
Another aspect of the present invention is characterized in that a liquid jet printing head, further includes a liquid resistant and high thermal conductive material disposed on the surface of heating elements on the heating element substrate to provide a wavy ramp surface.
The function of the invention will be described below.
Disposing a liquid resistant and high thermal conductive material on the surface of heating elements on the heating element substrate so as to provide a wavy ramp surface causes the surface area of the high thermal conductive material to be increased and causes the heat radiation of the heating element substrate to be improved.
Another aspect of the present invention is characterized in that a liquid jet printing head further includes the ramp of the high thermal conductive material exceeding a reference value being coated by the resin layer.
The function of the invention will be described below.
The portion with the ramp exceeding a reference value in the high thermal conductive material having a wavy ramp surface is not suitable for the deposition of the high thermal conductive material at a predetermined thickness. Therefore such a portion may have a potential risk of corrosion of the heating element substrate when contacting with the liquid. Therefore, by depositing a resin layer on the high thermal conductive material on the area where the thickness exceeds a reference value, the corrosion of the high thermal conductive material by the liquid in the defective deposition points of high thermal conductive material occurred in such area can be effectively prevented.
Another aspect of the present invention is characterized in that a liquid jet printing apparatus includes a liquid jet printing head in accordance with the present invention.
The function of the invention will be described below.
When using the liquid jet printing head in accordance with an aspect of the present invention, a liquid jet printing apparatus may perform stable liquid jet without the fear of bubbles generated. Also the heat radiation from the heating element substrate to the liquid will be prompted so that the increase of temperature in the heating element substrate may be well controlled so as to be able to continuously eject.
Another aspect of the present invention is characterized in that a liquid jet printing apparatus further includes the liquid jet printing head arranged so as to eject liquid in the angular range between the gravity direction and up to 45 degrees with respect to the gravity direction.
The function of the invention will be described below.
When a liquid jet printing head is arranged to eject liquid in the angular range between the gravity direction and 45 degrees from the gravity direction, the path from the inlet of a common chamber to the ink outlet should be accordingly disposed in the range between the gravity direction and 45 degrees from the gravity direction. Thus the bubbles generated in separate channels or the common chamber may displace toward the inlet of the common chamber. This may prevent the liquid jet through the separate channels from being affected.
Another aspect of the present invention is characterized in that a method of manufacturing a liquid jet printing head having a liquid channel substrate forming separate channels for jetting liquid and a portion of a common chamber for supplying liquid to the separate channels, in accordance with any one aspect of the present invention, wherein the liquid path substrate is made of a silicon substrate, on which grooves are formed for providing the separate channels and the common chamber by using either a crystalline anisotropic etching method or anisotropic etching method.
The function of the invention will be described below.
By forming grooves by either crystalline anisotropic etching or anisotropic etching of a silicon substrate, a portion of separate channels and a common chamber may be formed on a liquid path substrate at high precision.
Another aspect of the invention is characterized in that a method of manufacturing a liquid jet printing head includes a first step of etching a first surface of the liquid path substrate to provide grooves forming a portion of the separate channels and the common chamber, and a second step of processing the substrate from a second surface opposing to the first surface to decrease the thickness of the substrate to pierce there through the groove for a portion of the common chamber.
The function of the invention will be described below.
In general, a portion (pierced throughhole) of the common chamber of the path substrate is formed before forming the separate channels. Care should be taken for handling a path substrate on which the throughhole is formed at the time of forming separate channels; otherwise the substrate will be damaged. In the present invention, the process of forming separate channels is performed at the same time of process of grooves for a portion of the common chamber, and thereafter a portion of the common chamber may be pierced by for example grinding, as the final process of path substrate. This prevents the substrate from being damaged.
When forming throughhole on the path substrate prior to forming of separate channels, cooling gas for the channel process may be leaked from the second surface to the first surface, causing some degradation of process quality and precision of the separate channels. In accordance with the present invention, the quality and precision of process of separate channels may be improved by piercing a portion of common chamber by decreasing the thickness of substrate from the second surface side after the process of separate channels.
Another aspect of the present invention is characterized in that in a method of manufacturing a liquid jet printing head in accordance with the present invention, the second process step is performed after bonding the liquid path substrate and heating element substrate.
The function of the invention will be described below.
The liquid path substrate and heating element substrate will be bonded together after forming grooves for the separate channels and the like in the first surface side. Thereafter, a portion forming a common chamber will be pierced through the substrate by piercing therethrough from the second surface side of the liquid path substrate. In this manner, since the throughhole portion will be formed by processing from the second surface side after increasing the rigidity of the liquid path substrate by bonding the liquid path substrate with the heating element substrate, defects of substrates can be securely prevented.
Another aspect of the present invention is characterized in that a method of manufacturing a liquid jet printing head in accordance with any one of aspects provided by the present invention includes a heating element substrate incorporating heating elements, the heating element substrate being integrated with heating elements and driver circuits on the surface thereof by means of semiconductor manufacturing technique.
The function of the invention will be described below.
Forming heating elements and driver circuits integrated on a substrate may facilitate the forming process as well as improve the reliability of signal processing.
Additional features and advantages of the invention will be according to part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The above mentioned and other features and advantages of the invention may be implemented and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.